This invention pertains to inclined conveyor belt separating systems with a responsive, lower gas control arrangement. The separating systems are for separating spherically shaped rolling solids from irregularly-shaped nonrolling solids and are especially useful for oil shale retorting processes using spherically-shaped solid heat carriers which are recycled through the retorting process.
It is sometimes necessary, e.g., oil shale retorting with spherical heat carriers, to separate spherically-shaped rolling solids from irregularly-shaped rolling solids. The spherically-shaped solids are recovered while the irregularly-shaped solids are separated for disposal. There are many systems for separating solids which have significantly different sizes or particle weights, but there are relatively few ways of efficiently separating a large volume of solids having similar sizes and particle weights, especially when a dry, compact, high capacity, flexible separating system is required.
Copending application Ser. No. 749,505, filed Dec. 10, 1976, which is entitled "Separation and Recovery of Heat Carriers in an Oil Shale Retorting Process", and Ser. No. 749,587, filed Dec. 10, 1976, which is entitled "Inclined Conveyor Belt Solids Separation System", and which are owned by a common assignee and are incorporated herein, provide embodiments of elongated conveyor belt solids separating systems wherein the conveyor belt is appropriately inclined from horizontal along its longitudinal axis. Application Ser. No. 749,587 describes, among other things, upper and lower solids control arrangements and solids feed control measures.
The longitudinally inclined conveyor belt separating system requires smooth, continuous operation. It requires that a proper amount of spherically-shaped solids be maintained on the upper surface of the conveyor belt. Yet, in some cases, the mass flow rate of the solid, or the relative concentrations of the solids, or other conditions or combinations thereof, are likely to fluctuate on both a sporadic and a longer cyclic basis. These changes adversely affect the separating efficiency of the separating system or cause inefficient overdesign allowances. These fluctuations tend to create rapid channeling of rolling solids off the belt or waves of piled-up unseparated solids which pass up the surface of the belt and tend to flood the belt. When channeling occurs, unseparated nonrolling solids are carried off with the rolling solids. When flooding occurs and channeling is not used as a counteractive measure, spherically-shaped solids are carried over with the less valuable, irregularly-shaped solids.
This invention describes a responsive, easy to operate inclined conveyor belt separating system for maintaining the proper amount of spherically-shaped rolling solids on the conveyor belt while preventing channeling of the rolling solids off the belt and flooding of the belt by unseparated solids. Some enbodiments of this invention utilize some of the control measures described in the aforementioned application Ser. No. 749,587.